The latest violence did not affect production at the Grasberg mine, which accounts for nearly 40 percent of Freeport's total copper reserves and boasts the world's largest reserves, said company spokesman Mindo Pangaribuan.

"Nine people were injured. Three required hospitalization for treatment of injuries that are not life-threatening and the other six were released after treatment of minor injuries," Pangaribuan said in an e-mailed statement.

Police earlier said six people were wounded in the shooting on a highway leading to the mine.

The mine in insurgency-affected Papua has been a source of friction over its environmental impact and the share of revenues going to Papua.

One of the staff, James Lockhart, an American, was hit by flying glass near his left eye and had been flown to Singapore for treatment, Papua police spokesman Agus Rianto said.

"The attack happened around 6.30 in the morning. The investigation is underway," Mimika police chief Mochammad Sagi said.

A series of shootings by unidentified gunmen have taken place near the mine in recent months and at least two people have been killed.

The resource-rich province of Papua has suffered a low-level separatist insurgency for decades. The Grasberg mine is about 3,350 km (2,080 miles) east of Indonesia's capital Jakarta.